org.cryptimeleon.craco.protocols.arguments.sigma.schnorr.setmembership

Class SmallerThanPowerFragment

java.lang.Object

org.cryptimeleon.craco.protocols.arguments.sigma.schnorr.SendThenDelegateFragment

org.cryptimeleon.craco.protocols.arguments.sigma.schnorr.DelegateFragment

org.cryptimeleon.craco.protocols.arguments.sigma.schnorr.setmembership.SmallerThanPowerFragment

All Implemented Interfaces:

SchnorrFragment

public class SmallerThanPowerFragment
extends DelegateFragment

A fragment to prove a statement of the form \(0 \leq \text{member} < \text{base}^\text{power}\).

Nested Class Summary

Nested classes/interfaces inherited from class org.cryptimeleon.craco.protocols.arguments.sigma.schnorr.SendThenDelegateFragment

SendThenDelegateFragment.ProverSpec, SendThenDelegateFragment.ProverSpecBuilder, SendThenDelegateFragment.SendThenDelegateAnnouncement, SendThenDelegateFragment.SubprotocolSpec, SendThenDelegateFragment.SubprotocolSpecBuilder, SendThenDelegateFragment.WitnessValues

Field Summary

Fields

Modifier and Type	Field and Description
protected int	base
protected org.cryptimeleon.math.expressions.exponent.ExponentExpr	member
protected int	power
protected SetMembershipPublicParameters	pp

Constructor Summary

Constructors

Constructor and Description
SmallerThanPowerFragment(org.cryptimeleon.math.expressions.exponent.ExponentExpr member, int base, int power, SetMembershipPublicParameters pp) Instantiates the fragment.

Method Summary

Modifier and Type	Method and Description
static SetMembershipPublicParameters	generatePublicParameters(org.cryptimeleon.math.structures.groups.elliptic.BilinearGroup group, int base) Generates public parameters to use for a given base.
protected SendThenDelegateFragment.ProverSpec	provideProverSpecWithNoSendFirst(SchnorrVariableAssignment externalWitnesses, SendThenDelegateFragment.ProverSpecBuilder builder) Run by the prover to set up witness values for variables this fragment proves knowledge of itself (i.e.
protected SendThenDelegateFragment.SubprotocolSpec	provideSubprotocolSpec(SendThenDelegateFragment.SubprotocolSpecBuilder builder)

Methods inherited from class org.cryptimeleon.craco.protocols.arguments.sigma.schnorr.DelegateFragment

provideAdditionalCheck, provideProverSpec, provideSubprotocolSpec, restoreSendFirstValue, simulateSendFirstValue

Methods inherited from class org.cryptimeleon.craco.protocols.arguments.sigma.schnorr.SendThenDelegateFragment

checkTranscript, compressTranscript, debugFragment, decompressTranscript, generateAnnouncement, generateAnnouncementSecret, generateResponse, generateSimulatedTranscript, restoreAnnouncement, restoreResponse

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

base

protected final int base

power

protected final int power

member

protected final org.cryptimeleon.math.expressions.exponent.ExponentExpr member

pp

protected final SetMembershipPublicParameters pp

Constructor Detail

SmallerThanPowerFragment

public SmallerThanPowerFragment(org.cryptimeleon.math.expressions.exponent.ExponentExpr member,
                                int base,
                                int power,
                                SetMembershipPublicParameters pp)

Instantiates the fragment.

Parameters:

member - an expression whose value shall be between 0 and base^power (exclusive). In the easiest case, this is a SchnorrZnVariable, but it can be any affine linear combination of SchnorrZnVariables.

base - a number (generally the bigger this number, the bigger the public parameters but the shorter the proof)

power - a number (protocol computation and communication cost is linear in this number)

pp - honestly generated public parameters for a set membership proof for {0, ..., base-1}. Can be generated by generatePublicParameters(BilinearGroup, int)

Method Detail

generatePublicParameters

public static SetMembershipPublicParameters generatePublicParameters(org.cryptimeleon.math.structures.groups.elliptic.BilinearGroup group,
                                                                     int base)

Generates public parameters to use for a given base.

Parameters:

group - the group to use for this fragment

base - the desired base (see constructor)

provideProverSpecWithNoSendFirst

protected SendThenDelegateFragment.ProverSpec provideProverSpecWithNoSendFirst(SchnorrVariableAssignment externalWitnesses,
                                                                               SendThenDelegateFragment.ProverSpecBuilder builder)

Description copied from class: DelegateFragment

Run by the prover to set up witness values for variables this fragment proves knowledge of itself (i.e. those specified in DelegateFragment#provideSubprotocolSpec(SubprotocolSpecBuilder)).

A typical example implementation can be found in SmallerThanPowerFragment.

Specified by:

provideProverSpecWithNoSendFirst in class DelegateFragment

Parameters:

externalWitnesses - the witness values for external variables

builder - helper object to instantiate a ProverSpec

Returns:

the specification of witness values for this fragment's own variables. Returned by ProverSpecBuilder#build().

provideSubprotocolSpec

protected SendThenDelegateFragment.SubprotocolSpec provideSubprotocolSpec(SendThenDelegateFragment.SubprotocolSpecBuilder builder)

Specified by:

provideSubprotocolSpec in class DelegateFragment